Issa, 60, is the firebrand Republican chairman of the House Oversight and Government Reform Committee. He has hammered the Obama administration over its handling of the Benghazi attacks, the IRS and Veterans Affairs scandals, as well the troubled rollout of its heathcare.gov website and a host of other hot-button issues.
It has been up to Cummings, 63, the panel’s top Democrat, to be the first line of defense for the administration against these assaults.
The task has left Cummings battered by Issa and conservative pundits who have accused him of trying to shield White House illegalities. The chairman even accused his Democratic counterpart of throwing a "hissy fit" when things don't go his way.
But the role has catapulted the Marylander to hero status among Democrats, who have praised him for standing up to a lawmaker they see as a Republican bully more interested in bringing down the administration than conducting real investigations.
"He’d rather be playing offense than defense," said Jamie Raskin, a Democratic Maryland state senator who has worked with Cummings on political and policy matters for years. "But he’s a strong Democrat and he’s clearly willing to do what he needs to do to protect whatever forward motion we've got.”
It’s a responsibility Cummings has accepted, though one he wishes weren't necessary.
“This is not about me being a defender of the president. It’s about making sure the administration and witnesses … are treated fairly, because I think it goes to the integrity of the committee,” Cummings told the Washington Examiner.
When asked whether Issa was upholding the panel's integrity, Cummings said no. “Not when you've got a chairman who gets four Pinocchios,” he said, referring to a Washington Post Fact Checker rating suggesting that Issa wasn't truthful when criticizing former Secretary of State Hillary Clinton over the Benghazi attacks.
Cummings said Issa's persistent targeting of the Obama administration has been a "distraction" to the committee's mission to investigate potential wrongdoing throughout government, not just the executive branch.
“There's nothing wrong with looking at the IRS, there's nothing wrong with looking at Benghazi, all these issues," he said. "But why do you have to do multiple hearings on, say, the Affordable Care Act and do nothing on things that really are hurting people?"
He stopped short of saying Issa has abused his authority. "You’ll have to ask him what he thinks he should be doing,” he said.
Their contentious relationship came to a head in March, when Issa abruptly adjourned a hearing on the IRS scandal and turned off Cummings' microphone after a testy exchange. Issa later apologized, which Cummings accepted.
"I mourn for what could have been with regard to this committee," Cummings said of the panel since Issa took control in 2011. " ... We could’ve been better."
But he says he hasn't given up hope that the panel, as well as Congress, can return to bipartisanship as the norm, not the exception.
In his efforts to bridge the partisan divide, Cummings brokered several deals with Republicans, including a drug safety bill signed by President Obama that aims to deter price gouging and a whistleblower measure the committee passed with wide bipartisan support.
Cummings also recently invited Rep. Jason Chaffetz, who is vying to be the panel's top Republican when Issa steps down in January, to visit his working-class Baltimore district.
The outing was a success, Cummings said, because it exposed Chaffetz to issues largely foreign to his rural Utah district. Chaffetz in turn has invited Cummings to Utah in August.
“I always try to concentrate on not so much on who I’m fighting against, but what I’m fighting for," Cummings said. "If I can help somebody understand what I’m fighting for, maybe compromise becomes a little easier."
Cummings said he hopes the committee's next chairman — likely Chaffetz — will broaden the panel's investigative authority to focus on issues afflicting his district, like mortgage fraud and soaring pharmaceutical prices.
"For my constituents, it is very important that government function properly," he said. "They don’t have a lot of savings, but they have put money into the government through their taxes."
Cummings rose from similarly humble upbringings. The son of a sharecropper, he was raised in Baltimore and graduated from Howard University in Washington before getting a law degree from the University of Maryland. He served for 13 years in the Maryland House of Delegates before he was elected to Congress in 1996.
For the past 32 years, he has lived in the same house in inner-city Baltimore, near where much of the television series "The Wire" was filmed.
"There’s a lot of places I could live, but I live there to be a role model to little black kids," said Cummings, who has three children of his own. "I really want the children there to have as good a chance, or a better chance, than I had."
Cummings, who is married to Maya Rockeymoore, president of a Washington nonprofit that focuses on social change, said a recent visit to his great-great-grandparents' gravesite in South Carolina highlighted the need for him to continue his struggles on Capitol Hill.
“I stood there over the graves and I thought about how their great great-grandson is a member of Congress," he said. He said it was only because “some people believed in interpreting the Constitution” in a new way that “allowed me to be here in this institution that used to consider people like me a slave, three-fifths of a man."
"I don’t do this for me. This is bigger than me. This is for generations yet unborn. And I really mean that.”